Injection coal and coal blending method thereof
By synergistically blending high-sulfur pulverized coal, bituminous coal, and high-carbon dust, the problems of high pulverized coal injection cost and difficult resource utilization in blast furnaces have been solved, achieving efficient combustion and stable operation, reducing blast furnace production costs and ensuring the quality of molten iron.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- RIZHAO STEEL HLDG GROUP
- Filing Date
- 2026-02-02
- Publication Date
- 2026-05-19
AI Technical Summary
In existing blast furnace pulverized coal injection technology, the high dependence on low-sulfur coal leads to high costs, high-carbon dust is difficult to utilize as a resource, and the combustion performance of mixed pulverized coal is unstable, affecting the smooth operation of the blast furnace and the quality of molten iron.
High-sulfur pulverized coal, bituminous coal, and high-carbon dust collector ash are mixed in a preset mass ratio. The fixed carbon, calorific value, and sulfur content of the mixed coal powder are controlled. The high-carbon dust collector ash is burned first by bituminous coal to promote combustion, thereby achieving staged combustion, optimizing particle size and ash melting temperature, and ensuring burnout rate and fluidity.
It reduces the unit mass cost of pulverized coal injection, improves the combustion rate of mixed pulverized coal and the stability of blast furnace, realizes the stable resource utilization of high-carbon dust, and avoids environmental and site pressure.
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Abstract
Description
Technical Field
[0001] This invention relates to the technical field of pulverized coal ratio and utilization in blast furnace ironmaking, specifically to a pulverized coal injection method. Background Technology
[0002] With the development of pulverized coal injection technology in blast furnaces, the range of coal types used for pulverized coal injection has been continuously expanding. This includes high-quality pulverized coal with low sulfur content, high volatile matter, and low ash and moisture content, as well as lower-priced low-quality coal powder such as high-sulfur coal and bituminous coal, and byproducts such as high-carbon dust generated during ironmaking. Iron and steel plants typically employ a multi-coal mixed injection method to reduce pulverized coal injection costs while balancing combustion and metallurgical performance.
[0003] Among commonly used pulverized coal injections, low-sulfur coal has lower ash and sulfur content and higher calorific value, but its ignition temperature is relatively high and its combustion speed is relatively slow. Unburned coal powder is easily formed in the blast furnace tuyeres, affecting the smooth operation of the blast furnace. Bituminous coal has higher ash content but higher volatile matter content and lower ignition temperature, resulting in good combustibility. However, the calorific value of the pulverized coal is relatively low, and its use in large quantities will reduce the theoretical combustion temperature. High-sulfur coal is similar to low-sulfur coal in terms of ash content, volatile matter, and combustion characteristics, but its sulfur content is higher. Even if its calorific value is slightly higher than that of low-sulfur coal, it will increase the desulfurization burden on the blast furnace. High-carbon dust has the characteristics of high fixed carbon and ash content, extremely low volatile matter, low calorific value, and poor combustion performance. Direct injection in large quantities can easily lead to low burnout rate and slagging risk in the tuyeres area.
[0004] From a price perspective, the unit price of pulverized coal injection is closely related to the coal type and quality. Generally, the price is highest for low-sulfur coal, followed by high-sulfur coal (1.5% sulfur), then high-sulfur coal (1.0% sulfur), and finally the cheapest for bituminous coal. High-carbon dust is mainly a by-product recovered within the plant, involving only transportation and storage costs. With the tightening of high-quality low-sulfur coal resources and rising prices, continued heavy reliance on low-sulfur coal injection will significantly increase blast furnace production costs.
[0005] A statistical analysis of the composition of pulverized coal injected into the blast furnace at an ironmaking plant in 2023 and 2024 shows that the fixed carbon content is approximately 76%, the sulfur content is approximately 0.75%, and the dry basis higher calorific value is approximately 7600 kcal / kg, which is close to the lower limit allowed by the process. Under the current condition of a coke sulfur content of 0.65%–0.75%, continuing to rely solely on low-sulfur coal or increasing the proportion of low-sulfur coal will keep the injection cost high; on the other hand, simply increasing the proportion of high-sulfur coal may lead to an increase in the sulfur content of molten iron and a heavier desulfurization burden, which is not conducive to the low-cost and stable operation of the blast furnace.
[0006] Furthermore, iron and steel plants generate a large amount of high-carbon dust from their blast furnace and coke oven dust removal systems. This dust has a high carbon content, relatively low levels of harmful elements, and a good particle size distribution. If it cannot be effectively utilized, it occupies storage space and increases processing costs. How to achieve low-cost pulverized coal injection by synergistically utilizing low-cost resources such as high-sulfur coal, bituminous coal, and high-carbon dust without deteriorating the metallurgical performance of the blast furnace, while ensuring the combustion rate of the mixed pulverized coal and the quality of the molten iron, is a pressing issue that needs to be addressed in current blast furnace pulverized coal injection technology. Summary of the Invention
[0007] The purpose of this invention is to provide a pulverized coal injection method and its blending method to solve the problems of high dependence on low-sulfur coal, high injection cost, and difficulty in efficient resource utilization of high-carbon dust in existing pulverized coal injection, while ensuring smooth blast furnace operation and stable sulfur content in molten iron.
[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a method for blending pulverized coal, comprising the following steps: Step 1: Determine the benchmark technical indicators for the existing pulverized coal injection in the blast furnace. The benchmark technical indicators include: fixed carbon mass percentage ≥74%, sulfur mass percentage ≤0.75%, and dry basis higher calorific value ≥7600kcal / kg. Step 2: Provide high-sulfur pulverized coal, bituminous coal, and high-carbon dust, wherein: the sulfur content of the high-sulfur pulverized coal is approximately 1.5% by mass; the bituminous coal is high-volatile bituminous coal with a volatile matter content ≥35% by mass; and the high-carbon dust is coke dust. Step 3: Prepare high-sulfur pulverized coal, bituminous coal, and high-carbon dust ash pulverized coal from the high-sulfur pulverized coal, bituminous coal, and high-carbon dust ash pulverized coal to meet the particle size requirements for blast furnace injection, respectively. Step 4: Mix the high-sulfur pulverized coal, the bituminous coal, and the high-carbon dust removal ash coal according to a preset mass ratio to obtain mixed coal powder. The preset mass ratio satisfies the following: (1) The mass percentage of the high-carbon dust removal ash coal powder is 1% to 2%, the mass percentage of the bituminous coal powder is 11% to 18%, and the mass percentage of the high-carbon dust removal ash coal powder is less than the mass percentage of the bituminous coal powder. (2) The fixed carbon mass percentage of the mixed coal powder calculated according to the mass ratio is ≥74%, the dry basis high calorific value is ≥7600kcal / kg, and the sulfur mass percentage is ≤0.75%; Step 5: Use the mixed pulverized coal as blast furnace injection fuel.
[0009] Preferably, the high-carbon dust has a carbon content of ≥82.8% by mass and a particle size of ≥98% of particles smaller than 1mm by mass.
[0010] Preferably, the ignition point temperature of the bituminous coal powder is ≤320℃, and the ignition point temperature of the high-sulfur pulverized coal powder is ≥380℃.
[0011] Preferably, when determining the preset mass ratio, the unit mass cost of the mixed pulverized coal is limited to be lower than the unit mass cost when only low-sulfur pulverized coal is used as pulverized coal under the same injection conditions, and the sulfur mass fraction of blast furnace hot metal is limited to be no higher than 0.05% when the sulfur mass fraction of coke is 0.65% to 0.75%.
[0012] Preferably, the mass percentage of high-carbon dust removal ash coal powder in the mixed coal powder is 2%, the mass percentage of bituminous coal powder is 13%, and the remainder is high-sulfur pulverized coal powder.
[0013] Preferably, the ash melting temperature of the high-carbon dust is higher than the blast furnace hot blast temperature.
[0014] Preferably, in the process of preparing high-carbon dust removal pulverized coal, the high-carbon dust removal ash collected by the blast furnace or coke oven dust removal system is dried, and particles with a diameter greater than 1 mm are removed by sieving or air classification, and the mass percentage of particles with a diameter less than 1 mm in the remaining high-carbon dust removal ash is controlled to be not less than 98%.
[0015] A type of pulverized coal, prepared according to the aforementioned pulverized coal blending method, comprises high-sulfur pulverized coal powder, bituminous coal powder, and high-carbon dust-removing ash coal powder, wherein: The high-sulfur pulverized coal is produced from high-sulfur pulverized coal with a sulfur mass percentage of approximately 1.5%. The bituminous coal powder is obtained from bituminous coal with a volatile matter mass percentage of ≥35%; The high-carbon dust removal ash coal powder is obtained from coke dust removal ash, and the carbon content of the high-carbon dust removal ash coal powder is ≥82.8% by mass, and the mass percentage of particles with a particle size of less than 1 mm is ≥98%. The high-carbon dust-removing coal ash has a mass percentage content of 1% to 2%, the bituminous coal ash has a mass percentage content of 11% to 18%, and the mass percentage content of the high-carbon dust-removing coal ash is less than the mass percentage content of the bituminous coal ash. The mixed pulverized coal has a fixed carbon content of ≥74% by mass, a dry basis higher calorific value of ≥7600 kcal / kg, and a sulfur content of ≤0.75% by mass. Compared with existing technologies, the pulverized coal injection and its blending method using the above-mentioned technical solution have the following beneficial effects: I. By using high-sulfur pulverized coal, bituminous coal and high-carbon dust ash in a co-blending process while meeting the existing control targets for fixed carbon, calorific value and sulfur content, and controlling the mass percentage range of high-carbon dust ash and bituminous coal, the amount of high-priced low-sulfur coal used in the mixed pulverized coal is significantly reduced, thereby reducing the unit mass cost of pulverized coal without changing the main equipment of the blast furnace. Second, by selecting bituminous coal with high volatile matter content and low ignition temperature, and mixing it with high-sulfur pulverized coal with high ignition temperature and high-carbon dust ash with high fixed carbon content according to a preset ratio, the mixed coal powder forms a staged combustion process in the blast furnace tuyeres area, in which bituminous coal ignites first, followed by high-sulfur pulverized coal and high-carbon dust ash participating in combustion in sequence. This reduces the actual ignition temperature of the high-carbon dust ash, increases the overall burnout rate of the mixed coal powder, and ensures the thermal regime and smooth operation of the blast furnace. Third, by drying and particle size classification of high-carbon dust collector ash, controlling its carbon content and fineness, and selecting dust collector ash sources with ash melting temperatures higher than blast furnace hot blast temperatures, the resulting high-carbon dust collector ash coal powder has good fluidity and injectability, and is less prone to forming low-melting-point slag at and near the tuyeres, thereby achieving stable resource utilization of high-carbon dust collector ash and avoiding environmental and site pressures caused by large-scale stockpiling. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the method flow for an embodiment. Detailed Implementation
[0017] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0018] like Figure 1 As shown, a method for blending pulverized coal includes the following steps: Step 1: Determine the benchmark technical indicators for the existing pulverized coal injection in the blast furnace. The benchmark technical indicators include: fixed carbon mass percentage ≥74%, sulfur mass percentage ≤0.75%, and dry basis higher calorific value ≥7600kcal / kg. Step 2: Provide high-sulfur pulverized coal, bituminous coal, and high-carbon dust, wherein: the sulfur content of the high-sulfur pulverized coal is approximately 1.5% by mass; the bituminous coal is high-volatile bituminous coal with a volatile matter content ≥35% by mass; and the high-carbon dust is coke dust. Step 3: Prepare high-sulfur pulverized coal, bituminous coal, and high-carbon dust ash pulverized coal from the high-sulfur pulverized coal, bituminous coal, and high-carbon dust ash pulverized coal to meet the particle size requirements for blast furnace injection, respectively. Step 4: Mix the high-sulfur pulverized coal, the bituminous coal, and the high-carbon dust removal ash coal according to a preset mass ratio to obtain mixed coal powder. The preset mass ratio satisfies the following: (1) The mass percentage of the high-carbon dust removal ash coal powder is 1% to 2%, the mass percentage of the bituminous coal powder is 11% to 18%, and the mass percentage of the high-carbon dust removal ash coal powder is less than the mass percentage of the bituminous coal powder. (2) The fixed carbon mass percentage of the mixed coal powder calculated according to the mass ratio is ≥74%, the dry basis high calorific value is ≥7600kcal / kg, and the sulfur mass percentage is ≤0.75%; Step 5: Use the mixed pulverized coal as blast furnace injection fuel.
[0019] In one embodiment, to determine the baseline technical indicators in step one, industrial analysis and calorific value tests were conducted on the pulverized coal currently used in the ironmaking plant and the alternative raw coal. The fixed carbon, ash, volatile matter, sulfur content, and calorific value of different pulverized coal (including low-sulfur coal, high-sulfur coal (1.0% sulfur), high-sulfur coal (1.5% sulfur), bituminous coal, and high-carbon dust) are listed in Table 1 for different pulverized coal compositions.
[0020] Table 1 Different coal powder compositions
[0021] As shown in Table 1, low-sulfur coal has lower ash and sulfur content and higher calorific value; bituminous coal has higher ash content but higher volatile matter and lower ignition temperature, resulting in good combustibility; high-sulfur coal (1.5% sulfur) has higher fixed carbon but higher sulfur content; and high-carbon dust has higher ash and fixed carbon content and very low volatile matter.
[0022] Meanwhile, a statistical analysis was conducted on the mixed pulverized coal actually used in the ironmaking plant in 2023 and 2024, and the fixed carbon, ash, volatile matter, sulfur and dry basis high calorific value of the mixed pulverized coal were obtained, as shown in Table 2.
[0023] Table 2 Composition of Mixed Pulverized Coal in Ironmaking Plants
[0024] The results show that the existing mixed pulverized coal has a fixed carbon content of approximately 76% by mass, a sulfur content of approximately 0.75% by mass, and a dry basis higher calorific value of approximately 7600 kcal / kg, which is close to the lower limit allowed by the process. Therefore, this invention directly adopts the above-mentioned existing operating levels when setting the benchmark technical indicators, ensuring that the coal blending scheme of this invention achieves cost reduction without deteriorating the blast furnace operating conditions.
[0025] In steps two and three, the high-sulfur pulverized coal and bituminous coal are crushed, dried, and pulverized by a coal mill to ensure their particle size meets the blast furnace injection particle size requirements, for example, R90 < 15%. High-carbon dust is collected by the dust removal system, dried, and screened to remove large pieces of coke powder, ensuring that the percentage of particles smaller than 1 mm is not less than 98% to guarantee good flowability and injection adaptability. All the above pulverization and screening processes can be implemented using existing coal milling and dust removal equipment in the ironmaking plant without altering the main structure of the blast furnace.
[0026] In step four, a multi-compartment coal blending system is used to quantitatively feed high-sulfur pulverized coal, bituminous coal, and high-carbon dust-removing ash coal powder separately. The feed rate of each component is precisely controlled by a belt scale or screw scale, ensuring that the mass percentage of the three coal powders after mixing falls within the aforementioned preset mass ratio range. Online or offline testing confirms that the fixed carbon, calorific value, and sulfur content of the mixed coal powder meet the benchmark technical indicators. The mixing process can be completed in a closed mixing chamber using mechanical stirring or pneumatic circulation mixing. Afterward, the mixed coal powder is fed into the blast furnace tuyeres via an injection tank, mixed with hot air, and injected into the blast furnace, realizing the industrial application of the method of this invention.
[0027] like Figure 1 As shown, the high-carbon dust contains ≥82.8% carbon by mass and ≥98% particles with a particle size of less than 1 mm by mass.
[0028] In a preferred embodiment, the high-carbon dust collector ash is selected from the coking plant dust collector ash. To evaluate the applicability of different dust collector ash byproducts, elemental analysis was performed on coking plant dust collector ash, coking feed line dust collector ash, ore bin dust collector ash, blast furnace bag filter dust collector ash, and blast furnace gravity dust collector ash. The results are shown in Table 4, which analyzes the composition of dust collector ash from the steel section.
[0029] Table 4. Composition analysis of dust from the steel section (%)
[0030] As shown in Table 4, the carbon content of the dust collected in the coke oven is the highest, reaching over 82.8%, while the content of harmful elements such as Fe, alkali metal oxides, and Zn is relatively low, making it suitable for circulation within the blast furnace.
[0031] Furthermore, industrial analysis and calorific value testing were conducted on the coking yard dust and the currently used pulverized coal. The results are shown in Table 5, Industrial Analysis of Coking Yard Dust and Pulverized Coal.
[0032] Table 5 Industrial Analysis of Dust and Pulverized Coal from Coke Yards
[0033] As shown in Table 5, the ash from coke oven dust has high ash content, low volatile matter, and a calorific value slightly lower than that of pulverized coal injection, but its fixed carbon content is still above 80%. By adding drying and screening processes after the dust removal system, controlling the moisture content within the process requirements, and removing particles larger than 1 mm using screens or air classifiers, the mass percentage of particles smaller than 1 mm can reach or exceed 98%, thus meeting the aforementioned requirements for the fineness of high-carbon dust.
[0034] Therefore, the high-carbon dust in this embodiment not only meets the requirements of high carbon content and fineness, but also has low content of harmful elements and stable source, and can be used to achieve large-scale, high-value-added resource utilization using the coal blending method proposed in this invention.
[0035] like Figure 1 As shown, the ignition point temperature of the bituminous coal powder is ≤320℃, and the ignition point temperature of the high-sulfur pulverized coal powder is ≥380℃, so that the bituminous coal powder will preferentially ignite and release volatiles during the blast furnace injection process, thereby reducing the ignition temperature of the high-carbon dust-removing ash coal powder by at least 50℃, thus promoting the combustion of the high-carbon dust-removing ash coal powder.
[0036] In one embodiment, the ignition characteristics of different pulverized coals were tested using a thermogravimetric analyzer and a blast furnace heating test. Specifically, standard samples were prepared from bituminous coal pulverized coal and high-sulfur pulverized coal pulverized coal, respectively. Heating and combustion experiments were conducted under controlled heating rates and atmosphere conditions. The ignition temperature was determined by the temperature of the sudden increase in the mass loss rate or the temperature at which the flame appeared. The test results showed that the ignition temperature of the bituminous coal pulverized coal used in this embodiment was no higher than 320℃, while the ignition temperature of the high-sulfur pulverized coal pulverized coal was significantly higher than that of the bituminous coal pulverized coal.
[0037] After the mixed pulverized coal is injected into the high-temperature, oxygen-rich zone before the blast furnace tuyeres, the low ignition point of the bituminous coal pulverized coal preferentially ignites under the action of the high-temperature hot air, rapidly releasing volatiles and forming a localized high-temperature, high-reducing atmosphere and strong turbulence, surrounding the unignited high-carbon dust ash pulverized coal particles. Comparative combustion experiments show that with the assistance of bituminous coal pulverized coal, the actual ignition temperature of the high-carbon dust ash pulverized coal is at least 50°C lower than when injected alone, and the burnout rate is significantly improved. This mechanism by which low-ignition-point coal promotes the combustion of high-carbon dust ash is consistent with the physicochemical characteristics of bituminous coal (high volatiles, low ignition temperature) and high-carbon dust ash (extremely low volatiles) shown in Table 1, thus explaining the role of bituminous coal pulverized coal in promoting the combustion of high-carbon dust ash pulverized coal.
[0038] like Figure 1As shown, when determining the preset mass ratio, the unit mass cost of the mixed pulverized coal is limited to be lower than the unit mass cost when only low-sulfur pulverized coal is used as pulverized coal under the same injection conditions, and the sulfur mass fraction of blast furnace hot metal is limited to not higher than 0.05% when the sulfur mass fraction of coke is 0.65% to 0.75%.
[0039] In one embodiment, a coal blending test was first conducted on bituminous coal and high-sulfur pulverized coal with different sulfur contents without adding high-carbon dust, and a variety of coal blending schemes were obtained. The composition and cost of the mixed coal powder are shown in Table 3. Bituminous coal mixed with high-sulfur coal.
[0040] Table 3. Mixed high-sulfur coal from bituminous coal.
[0041] As shown in Table 3, under the premise of meeting the constraints of fixed carbon and sulfur content, by increasing the proportion of bituminous coal and appropriately adjusting the proportion of high-sulfur coal (1.0% sulfur and 1.5% sulfur), a scheme with higher volatile matter, higher calorific value and lower unit coal powder cost can be obtained. Among them, the coal powder cost of one scheme is reduced by about RMB 1.3 / t compared with the reference scheme.
[0042] Based on this, 1% to 2% of high-carbon dust was introduced to conduct coal blending tests, and coal blending schemes with different blending ratios were obtained, as shown in Table 6, which shows the coal blending experiments that consumed coke oven dust.
[0043] Table 6 shows the coal blending experiment for consuming coke oven dust.
[0044] Comparing the existing mixed coal powder costs in Table 2 for 2023-2024 with the mixed coal powder costs of various schemes in Tables 3 and 6, it can be seen that the preset mass ratio scheme selected in this invention, under the premise that the carbon, calorific value and sulfur content meet the benchmark indicators, has a lower unit mass cost than the traditional scheme that only uses low-sulfur pulverized coal.
[0045] Meanwhile, through statistical analysis of long-term blast furnace operation data, under the existing conditions of coke sulfur mass percentage of 0.65% to 0.75%, the sulfur mass percentage of molten iron using the coal blending scheme of this invention can still be stably controlled below 0.05%, without significant increase in desulfurization burden or increased fluctuation in molten iron sulfur content. This indicates that the existing process control requirements can be met in terms of both injection cost and molten iron sulfur content.
[0046] like Figure 1 As shown, the mass percentage of high-carbon dust removal ash coal powder in the mixed coal powder is 2%, the mass percentage of bituminous coal powder is 13%, and the remainder is high-sulfur pulverized coal powder.
[0047] In a preferred embodiment, the mixed coal powder ratio is selected as follows: 2% by mass of high-carbon dust removal ash coal powder, 13% by mass of bituminous coal powder, and the remainder is high-sulfur pulverized coal powder. This ratio corresponds to a certain coal blending scheme in Table 6 (e.g., Scheme 3), and the fixed carbon, ash, volatile matter, total sulfur, and calorific value of its mixed coal powder are all listed in Table 6. As can be seen from the data in Table 6, under the above ratio conditions, the fixed carbon content of the mixed coal powder remains at approximately 74%, the dry basis higher heating value is approximately 7610 kcal / kg, and the sulfur content is not higher than 0.75%, meeting the requirements of the aforementioned benchmark technical indicators.
[0048] Meanwhile, as shown in Table 6, the coal powder cost of this formulation is the lowest among all candidate formulations. It can achieve a high blending and effective consumption of high-carbon dust, without significantly reducing the combustion performance of the mixed coal powder. It is a preferred implementation method that balances economy and metallurgical performance.
[0049] like Figure 1 As shown, the ash melting temperature of the high-carbon dust collector ash is higher than the blast furnace hot blast temperature, so that coking will not occur in or near the blast furnace tuyeres when the high-carbon dust collector ash pulverized coal is injected.
[0050] In one embodiment, the ash fusion properties of coke oven dust samples were tested, and the softening temperature, hemispherical temperature, and flow temperature of the ash were determined according to metallurgical industry standards. The test results showed that the flow temperature of the coke oven dust was higher than the upper limit of the blast furnace hot blast temperature (e.g., 1150℃~1250℃), typically above 1300℃. Combined with the low Fe content and moderate alkali metal content in Table 4, it can be determined that this high-carbon dust is unlikely to form low-melting-point eutectic in and around the blast furnace tuyeres.
[0051] In industrial applications, regular inspections of the injection system revealed no significant coking or slag buildup around the tuyeres; slag fluidity and composition analysis also showed no abnormal increase in viscosity, indicating that the selected high-carbon dust collector ash has a higher ash melting temperature than the blast furnace hot blast temperature, which helps to avoid tuyer blockage and unstable combustion.
[0052] like Figure 1 As shown, in the process of preparing high-carbon dust removal pulverized coal, the high-carbon dust removal ash collected by the blast furnace or coke oven dust removal system is dried, and particles with a diameter greater than 1 mm are removed by sieving or air classification, and the mass percentage of particles with a diameter less than 1 mm in the remaining high-carbon dust removal ash is controlled to be no less than 98%.
[0053] In one embodiment, the preparation of high-carbon dust in step three specifically includes the following process: the raw high-carbon dust collected by the blast furnace or coke oven dust removal system is fed into a drying device via a bucket elevator or a closed conveyor for drying. The drying device can be a rotary dryer, a fluidized bed dryer, or other conventional industrial drying equipment. Under the conditions of a hot air temperature of 100℃~200℃ and a material residence time of 20min~60min, the moisture content in the high-carbon dust is controlled within the process requirements, for example, a mass percentage content ≤1.0%, to avoid excessive moisture causing material agglomeration or blockage during the blowing process. After drying, the high-carbon dust is cooled and then sent to a screening or air classification unit, where particles larger than 1mm and entrained large pieces of coke powder are removed by a vibrating screen or a multi-stage air classification device. When screening, a sieve with a 1mm aperture can be used. When air classifying, the wind speed and the particle size can be adjusted to ensure that the mass percentage of particles smaller than 1mm in the high-carbon dust collected after screening or air classification is not less than 98%.
[0054] Particle size can be detected using a laser particle size analyzer or sieving test. After confirming that the particle size distribution meets the above requirements, the high-carbon dust collector ash is then fed into the coal blending system together with pulverized bituminous coal powder and high-sulfur pulverized coal powder for quantitative proportioning. Through the above drying and sieving / air classification treatment, on the one hand, the moisture and coarse particle content in the high-carbon dust collector ash can be significantly reduced, ensuring that the material has good flowability and injectability. On the other hand, without changing the high carbon content, the proportion of fine particles is increased, which is conducive to their rapid heating and combustion in the blast furnace tuyeres area, thereby improving the overall combustion rate of the mixed coal powder.
[0055] like Figure 1 As shown, the mixed pulverized coal for blast furnace injection obtained according to the above-described pulverized coal blending method consists of high-sulfur pulverized coal, bituminous coal, and high-carbon dust removal ash pulverized coal, wherein: The high-sulfur pulverized coal is produced from high-sulfur pulverized coal with a sulfur mass percentage of approximately 1.5%. The bituminous coal powder is obtained from bituminous coal with a volatile matter mass percentage of ≥35%; The high-carbon dust removal ash coal powder is obtained from coke dust removal ash, and the carbon content of the high-carbon dust removal ash coal powder is ≥82.8% by mass, and the mass percentage of particles with a particle size of less than 1 mm is ≥98%. The high-carbon dust-removing coal ash has a mass percentage content of 1% to 2%, the bituminous coal ash has a mass percentage content of 11% to 18%, and the mass percentage content of the high-carbon dust-removing coal ash is less than the mass percentage content of the bituminous coal ash. The mixed pulverized coal has a fixed carbon content of ≥74% by mass, a dry basis higher calorific value of ≥7600 kcal / kg, and a sulfur content of ≤0.75% by mass.
[0056] In one embodiment, the typical physicochemical properties of the mixed coal powder obtained by the above-described coal blending method can be comprehensively reflected by Tables 1 and 4 to 6. Table 1 shows the approximate fixed carbon, ash, volatile matter, and sulfur levels of the candidate coal types; Tables 4 and 5 illustrate the elemental composition and industrial analysis results of high-carbon dust; and Table 6 shows the comprehensive properties of the mixed coal powder obtained under different blending ratios.
[0057] For example, when the mass percentage of high-carbon dust-collecting pulverized coal is 2% and the mass percentage of bituminous coal pulverized coal is 13%, the resulting mixed pulverized coal has a fixed carbon mass percentage of approximately 74%, a dry basis higher calorific value of approximately 7610 kcal / kg, and a sulfur mass percentage of approximately 0.73%, meeting the aforementioned requirements for the composition and performance of the mixed pulverized coal. This mixed pulverized coal exhibits good fluidity, burnout rate, and stability during blast furnace injection and can be directly supplied as commercial pulverized coal or consumed within the plant.
[0058] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for blending pulverized coal, characterized in that, Includes the following steps: Step 1: Determine the benchmark technical indicators for the existing pulverized coal injection in the blast furnace. The benchmark technical indicators include: fixed carbon mass percentage ≥74%, sulfur mass percentage ≤0.75%, and dry basis higher calorific value ≥7600kcal / kg. Step 2: Provide high-sulfur pulverized coal, bituminous coal, and high-carbon dust, wherein: the sulfur content of the high-sulfur pulverized coal is approximately 1.5% by mass; the bituminous coal is high-volatile bituminous coal with a volatile matter content ≥35% by mass; and the high-carbon dust is coke dust. Step 3: Prepare high-sulfur pulverized coal, bituminous coal, and high-carbon dust ash pulverized coal from the high-sulfur pulverized coal, bituminous coal, and high-carbon dust ash pulverized coal to meet the particle size requirements for blast furnace injection, respectively. Step 4: Mix the high-sulfur pulverized coal, the bituminous coal, and the high-carbon dust removal ash coal according to a preset mass ratio to obtain mixed coal powder. The preset mass ratio satisfies the following: (1) The mass percentage of the high-carbon dust removal ash coal powder is 1% to 2%, the mass percentage of the bituminous coal powder is 11% to 18%, and the mass percentage of the high-carbon dust removal ash coal powder is less than the mass percentage of the bituminous coal powder. (2) The fixed carbon mass percentage of the mixed coal powder calculated according to the mass ratio is ≥74%, the dry basis high calorific value is ≥7600kcal / kg, and the sulfur mass percentage is ≤0.75%; Step 5: Use the mixed pulverized coal as blast furnace injection fuel.
2. The method for blending pulverized coal according to claim 1, characterized in that: The high-carbon dust has a carbon content of ≥82.8% by mass and a particle size of ≥98% of particles smaller than 1mm.
3. The method for blending pulverized coal according to claim 2, characterized in that: The ignition point temperature of the bituminous coal powder is ≤320℃, and the ignition point temperature of the high-sulfur pulverized coal powder is ≥380℃.
4. The method for blending pulverized coal according to claim 3, characterized in that: When determining the preset mass ratio, the unit mass cost of the mixed pulverized coal is limited to be lower than the unit mass cost when only low-sulfur pulverized coal is used as pulverized coal under the same injection conditions, and the sulfur mass fraction of blast furnace hot metal is limited to not higher than 0.05% when the sulfur mass fraction of coke is 0.65% to 0.75%.
5. A method for blending pulverized coal according to claim 4, characterized in that: The mixed coal powder contains 2% high-carbon dust removal ash coal powder by mass, 13% bituminous coal powder by mass, and the remainder is high-sulfur pulverized coal powder.
6. A method for blending pulverized coal according to claim 5, characterized in that: The ash melting temperature of the high-carbon dust is higher than that of the blast furnace hot blast.
7. The method for blending pulverized coal according to claim 1, characterized in that: In the process of preparing high-carbon dust removal pulverized coal, the high-carbon dust removal ash collected by the blast furnace or coke oven dust removal system is dried, and particles with a diameter greater than 1 mm are removed by sieving or air classification, and the mass percentage of particles with a diameter less than 1 mm in the remaining high-carbon dust removal ash is controlled to be no less than 98%.
8. A type of pulverized coal, suitable for preparation by the pulverized coal blending method according to any one of claims 1 to 7, characterized in that: It consists of high-sulfur pulverized coal, bituminous coal, and high-carbon dust-removing ash, wherein: The high-sulfur pulverized coal is produced from high-sulfur pulverized coal with a sulfur mass percentage of approximately 1.5%. The bituminous coal powder is obtained from bituminous coal with a volatile matter mass percentage of ≥35%; The high-carbon dust removal ash coal powder is obtained from coke dust removal ash, and the carbon content of the high-carbon dust removal ash coal powder is ≥82.8% by mass, and the mass percentage of particles with a particle size of less than 1 mm is ≥98%. The high-carbon dust-removing coal ash has a mass percentage content of 1% to 2%, the bituminous coal ash has a mass percentage content of 11% to 18%, and the mass percentage content of the high-carbon dust-removing coal ash is less than the mass percentage content of the bituminous coal ash. The mixed pulverized coal has a fixed carbon content of ≥74% by mass, a dry basis higher calorific value of ≥7600 kcal / kg, and a sulfur content of ≤0.75% by mass.